Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
Abundance analysis of prime B-type targets for asteroseismology. II. B6-B9.5 stars in the field of view of the CoRoT satellite
Context: Aims: The main goal of the ground-based seismologysupport program for the CoRoT mission was to obtain photometric andspectroscopic data for stars in the fields monitored by the satellite.These ground-based observations were collected in the GAUDI archive.High-resolution spectra of more than 200 B-type stars are available inthis database, and about 45% of them is analysed here. Methods:To derive the effective temperature of the stars, we used photometricindices. Surface gravities were obtained by comparing observed andtheoretical Balmer line profiles. To determine the chemical abundancesand rotational velocities, we used a spectrum synthesis method, whichconsisted of comparing the observed spectrum with theoretical ones basedon the assumption of LTE. Results: Atmospheric parameters,chemical abundances, and rotational velocities were determined for 89late-B stars. The dominant species in their spectra are iron-peakelements. The average Fe abundance is 7.24 ± 0.45 dex. Theaverage rotational velocity is 126 km s-1, but there are 13and 20 stars with low and moderate V sin i values, respectively. Theanalysis of this sample of 89 late B-type stars reveals many chemicallypeculiar (CP) stars. Some of them were previously known, but at least 9new CP candidates, among which at least two HgMn stars, are identifiedin our study. These CP stars as a group exhibit V sin i values lowerthan the stars with normal surface chemical composition.Atmospheric parameters and abundance analysis results are only availablein electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/506/213 The CoRoT spacemission was developed and is operated by the French space agency CNES,with participation of ESA's RSSD and Science Programmes, Austria,Belgium, Brazil, Germany, and Spain. Tables [see full textsee full text]and [see full textsee full text] are only available in electronic format http://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The proper motions of fundamental stars. I. 1535 stars from the Basic FK5
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP stars
The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhoodhas been constructed using astrometric data from Hipparcos satellite aswell as photometric and radial velocity data. The LM method\cite{luri95,luri96} allows the use of proper motion and radial velocitydata in addition to the trigonometric parallaxes to obtain luminositycalibrations and improved distances estimates. Six types of Bp - Apstars have been examined: He-rich, He-weak, HgMn, Si, Si+ and SrCrEu.Most Bp - Ap stars lie on the main sequence occupying the whole width ofit (about 2 mag), just like normal stars in the same range of spectraltypes. Their kinematic behaviour is typical of thin disk stars youngerthan about 1 Gyr. A few stars found to be high above the galactic planeor to have a high velocity are briefly discussed. Based on data from theESA Hipparcos astrometry satellite and photometric data collected in theGeneva system at ESO, La Silla (Chile) and at Jungfraujoch andGornergrat Observatories (Switzerland). Tables 3 and 4 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Systematic Errors in the FK5 Catalog as Derived from CCD Observations in the Extragalactic Reference Frame.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114..850S&db_key=AST
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| CCD observations linking the radio and optical references frames
Observations made with the U.S. Naval Observatory 20 cm transittelescope are presented for 104 FK5 and 13 radio stars that are directlytied into the J2000 extragalactic reference system. A comparison of thestar positions presented in this paper with the FK5 catalog findspossible warps in the FK5 reference system with amplitudes approximately0.1 arcsec and rotations for linking the optical and radio referencesystems with values omegax=-20 plus or minus 17 (s.e.),omegay=28 plus or minus 16 (s.e.), and omegaz=11plus or minus 13 (s.e.) mas. When the data of this paper are combinedwith other studies, these rotations become omegax=11 plus orminus 13 (s.e.), omegay=40 plus or minus 13 (s.e.), andomegaz=17 plus or minus 9 (s.e.) mas, indicating theomegay rotation might be real. Among the radio stars, thereare four stars (KQ Pup, 54 Cam, SZ Psc, and HD 244085) with significantoptical-radio offsets that exceed 0.15 arcsec in magnitude. Moreover,many other radio stars probably have appreciable offsets as determinedfrom a statistical investigation. Optical-radio offsets which aretypically accurate to sigma approximately plus or minus 42 (s.e.) masare also presented for 48 extragalactic objects observed with thetransit telescope. Among these objects, 21% have significant offsets.Radio galaxies are much more likely to have large offsets than QSOs andBL Lac objects, making many of them poor candidates for radio referenceobjects.
| Physical data of the fundamental stars.
Not Available
| Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
| A study of visual double stars with early type primaries. IV Astrophysical data
Astrophysical parameters (MK class, color excess, absolute magnitude,distance, effective temperature, mass, and age) are derived fromcalibrations of the uvby-beta indices for the members of 253 doublestars with O or B type primaries and faint secondaries. The photometricspectral classification is compared to the MK classes, and the agreementis very good. The derived data together with spectroscopic and JHKL dataare used for deciding which pairs are likely to be physical and whichare optical, and it is shown that 98 (34 percent) of the secondaries arelikely to be members of physical systems. For 90 percent of the physicalpairs the projected separation between the components is less than25,000 AU. A majority of the physical secondaries are late-type stars,and 50 percent of them are contracting towards the zero-agemain-sequence. Also presented are new uvby-beta data for 43 secondariesand a computer program for determining astrophysical parameters fromuvby-beta data.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| Confirmation among visual multiples of an increase of AP stars with age
Open clusters with ages below certain threshold values contain no Apstars and those with greater ages contain numbers of Ap stars thatapparently increase with age. But in view of the few young clustersstudied, the data could also be interpreted in terms of randomdifferences in the frequencies of Ap stars between individual clusters,rather than an age effect. Data on 77 field visual multiple systems(that originated from many different clusters and associations) in whichthe primaries are O5-A1 stars and the secondaries occur in the absolutemagnitude range of the Ap stars were, therefore, obtained. Againspectral classification shows no Ap stars in systems with ages notgreater than 1,000,000 yr and a steady increase in Ap stars thereafter.The numerical agreement with the cluster data is good, confirming thatthe cluster data are exhibiting a real age effect.
| A study of visual double stars with early type primaries. II - Photometric results
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&AS...51..161L&db_key=AST
| A study of visual double stars with early type primaries. I - Spectroscopic results
Attention is given to spectral peculiarities found in data on thespectral classes of 486 stars in 254 visual doublet or multiplet systemswith O or B type primaries, in order to isolate a group of very youngstars that may serve for the study of early stellar evolutioncharacteristics. It is noted that the material contains a substantialfraction of secondaries that are likely to be physical, and that severalof these may be in the premain-sequence phase of stellar evolution, orhave reached the zero-age main sequence.
| Visual multiples. VII - MK classifications
Classifications are given for 865 components of visual multiples; theyshow no systematic differences from the MK system, and the random errorsare one subclass in type and two-thirds of a luminosity class. It isfound that at least 1% of the F-type IV and V stars are weak-lined, 32%of the A4-F1 IV and V stars are Am, and 5% of the A0-A3 IV and V starsare early-type Am. Attention is called to the large fraction (55%) ofthe A3-A9 III-V stars that are of luminosity classes III or IV, unlikethe percentage (16%) at neighboring types.
| Four-colour UVBY and H-beta photometry of field stars - Double-lined spectroscopic binaries, G type dwarfs and early type FK4 stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...29..313O&db_key=AST
| Not Available
Not Available
| A spectroscopic investigation of visual binaries with B-type primaries.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74.1082M&db_key=AST
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Vízöntő |
| Rektaszcenzió: | 19h06m35.12s |
| Deklináció: | -01°20'46.1" |
| Vizuális fényesség: | 6.822 |
| Távolság: | 495.05 parszek |
| RA sajátmozgás: | 1 |
| Dec sajátmozgás: | -12.6 |
| B-T magnitude: | 6.89 |
| V-T magnitude: | 6.828 |
Katalógusok és elnevezések:
|
